The techniques for sending/receiving digital signals in multiple-antenna systems have many advantages, especially for the mobile access network. In particular, such techniques enable an increase in the bit-rate and/or reliability of the transmission in the context of a wireless communication.
There is a known technique of transmission in the prior art well suited to MIMO systems in which the transmission channel varies. This technique, also known as link adaptation, consists in adapting the resources used when sending as a function of a piece of information representing the transmission channel. This technique therefore calls for feedback between the receiver and the sender, providing the sender with the knowledge (generally partial knowledge) of the transmission channel.
In particular, this link adaptation can be dynamic and makes it possible to adapt to instantaneous variations in the transmission channel, by seeking to maximize the bit-rate of the radio link while at the same time complying with a certain quality of service requirement, such as for example a maximum bit-error rate.
To this end, the MCS (Modulation and Coding Scheme) assigned to each sending antenna, i.e. each data stream, and optionally the sending power values allocated to each data stream are modified. It may be recalled that, in a multiple-antenna system, the source signal to be sent is sent in the form of a set of data streams between the send antennas and the receive antennas.
The document by P. Layec, R. Visoz, and A. O. Berthet, “Achieving High Spectral Efficiency with Adaptive Layered Space Time Codes under Rate Control” (ICC 2007-IEEE) presents especially a multiple-antenna transmission system implementing the dynamic link adaptation method. In this technique, a space-time encoding is combined with a PARC (Per Antenna Rate Control) type of architecture implementing per antenna rate control. It may be recalled that the term “rate” classically is understood to mean a choice of modulation and encoding scheme (MCS), i.e. it comprises:                the rate of the channel code: for example ¼, ⅓, ½, etc;        the order of the modulation chosen, for example BPSK (binary phase-shift keying), QPSK (Quadrature PSK), 16QAM (16-quadrature amplitude modulation) type modulation etc.        
More specifically, the technique presented in the above-mentioned document assumes that there is a set of discrete rate values available. Conversely, it may be recalled that the results of information theory are based on infinite precision of rates and sending power values, thus assuming an infinite feedback link which is unachievable in practice.
In order to compensate for the deterioration in the capacity generated by the discretization operation, this prior art technique seeks to jointly optimize the discrete rates and the power value allocated to each sending antenna, in distributing the sending antennas among groups of antennas.
Thus, a receiver can determine the MCS (or discrete rate values) per group of antennas to be used in sending mode to minimize the difference with the theoretical performance values on the basis of knowledge of a family of MCS schemes available in sending mode (according to the sending standard for example) and transmit these elements to the sender in a feedback path, for example in a CQI (channel quality indicator) message.
The transmission system thus has adaptive distribution from an uplink of information to another, in order to combat quantification noise, or a distribution that is well defined during the configuration of the system and fixed throughout the duration of the transmission of the system.
However, one drawback of this prior art technique is that it relies on the assumption of a transmission of data streams that is independent per sending antenna, i.e. that the covariance matrix of the signal to be transmitted is diagonal, thus generating interference between the data streams.